SCLEROTINIA ROT OF PEARS IN OREGON

Record rainfall occurred in the Hood River Valley during spring of 199 3. In late spring, lesions up to 2 cm in diameter were observed on d'A njou pear pear fruitlets on the calyx end or where senescent flower pa rts adhered to the fruits. Sclerotinia sclerotiorum was consistently i solated from infected tissue. Koch's postulates were tested, and S. sc lerotiorum was confirmed as the cause of the disease. Mycelial growth of the pathogen on acidified potato dextrose afar was optimum at 20 de grees C, and the average growth rate was about 10 mm per day. Five pea r cultivars were ranked in order of increasing resistance to Sclerotin ia rot as follows: d'Anjou, Bosc, Columbia Red d'Anjou, Bartlett, and Comice. Among eight fungicides tested, only iprodione provided good co ntrol of fruit infection.